Method of forming a graphene device using polymer material as a support for a graphene film

ABSTRACT

The invention concerns a method of forming a graphene device, the method comprising: forming a graphene film ( 100 ) over a substrate; depositing, by gas phase deposition, a polymer material covering a surface of the graphene film ( 100 ); and removing the substrate from the graphene film ( 100 ), wherein the polymer material forms a support ( 102 ) for the graphene film ( 100 ).

FIELD

The present disclosure relates to the field devices partially formed ofgraphene, and to a method of forming a graphene device.

BACKGROUND

Graphene is a substance composed of carbon atoms forming a crystallattice one atom in thickness. Various applications have been proposedfor graphene, including its use in radio-frequency transistors and forforming transparent highly conductive and flexible electrodes, such asfor displays. It is of particular benefit in applications where highmobility conductors are desired. Most applications of graphene require amacroscale-sized graphene layer, comprising one or a few layers ofcarbon atoms, which is transferred onto a substrate of a materialselected based on the particular application.

Graphene is generally formed using a chemical vapor deposition (CVD)process, wherein graphene is deposited over a base substrate such as acopper foil. However, a difficulty is that it is relatively difficult toremove the graphene layer from the base substrate without damaging orpolluting the graphene layer and/or degrading its conductivity.

Furthermore, in some embodiments it would be desirable to provide amethod of forming a three-dimensional (3D) graphene device.

There is thus a need in the art for an improved method of forming agraphene device, and to one or more graphene devices formed based onsuch a method.

SUMMARY

It is an aim of embodiments of the present disclosure to at leastpartially address one or more needs in the prior art.

According to one aspect, there is provided a method of forming agraphene device, the method comprising: forming a graphene film over asubstrate; depositing, by gas phase deposition, a polymer materialcovering a surface of the graphene film; and removing the substrate fromthe graphene film, wherein the polymer material forms a support for thegraphene film.

According to one embodiment, the polymer material comprises a polymerfrom the n-xylylene family.

According to one embodiment, the polymer material comprises parylene.

According to one embodiment, the polymer layer is deposited with athickness of between 10 nm and 5 mm.

According to one embodiment, the graphene film is formed over athree-dimensional surface of the substrate.

According to one embodiment, removing the substrate from the graphenefilm is performed by a process of electrochemical delamination or usingan acid etch.

According to one embodiment, the above method of forming a graphenedevice is used for forming a sensor device that is to be placed over athree-dimensional form, wherein the substrate on which the graphene filmis formed comprises a mold having the shape of a three-dimensional form.

According to one embodiment, the mold is formed of a first material andat least one zone of a second material. During the formation of thegraphene film, graphene selectively forms only on the at least one zoneof the second material, and the polymer material is deposited over thegraphene film and at least a portion of the first material.

According to one embodiment, the method further comprises performing afurther gas phase deposition of the polymer material to encapsulate thegraphene film, after removing the substrate from the graphene film.

According to one embodiment, the graphene film is deposited to form aconductive track. The conductive track has a meandering form in adetection zone.

According to one embodiment, the graphene film is deposited in the formof a first plate of graphene formed in a detection zone and connected toa first conductive track. In addition, the method further comprisesforming a further graphene film covered by a further deposition ofpolymer material, wherein the further graphene film is deposited in theform of a second plate of graphene. The first and second graphene filmsare assembled such that the first and second graphene plates form acapacitive interface in the detection zone separated by a layer of thepolymer material.

According to a further aspect, there is provided a sensor devicecomprising a graphene film covered on at least one side by a polymermaterial. The polymer material has a detection element formed of agraphene film on a portion of its inside surface. The polymer materialcontacts and supports the graphene film.

According to one embodiment, the detection element comprises ameandering conductive track formed in a detection zone. The detectionelement electrically connects a first conductive track to a secondconductive track.

According to one embodiment, the detection element comprises first andsecond graphene plates at least partially overlapping each other. Thefirst graphene plate is connected to a first conductive track, and thesecond graphene plate is connected to a second conductive track.

According to one embodiment, the graphene device further comprises adetection circuit coupled to the first and second conductive tracks.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages will become apparentfrom the following detailed description of embodiments, given by way ofillustration and not limitation with reference to the accompanyingdrawings, in which:

FIG. 1 is a cross-section view of a graphene device according to anexample embodiment of the present disclosure;

FIG. 2 schematically illustrates an apparatus for forming a graphenedevice according to an example embodiment of the present disclosure;

FIGS. 3A to 3C are cross-section views of the formation of a graphenedevice according to an embodiment of the present disclosure;

FIGS. 4A to 4C are cross-section views of the formation of a 3D graphenedevice according to an embodiment of the present disclosure;

FIG. 5A illustrates a sensing device comprising graphene according to anexample embodiment of the present disclosure;

FIGS. 5B to 5D are cross-section views showing steps in a method offorming the sensing device of FIG. 5A according to an exampleembodiment;

FIG. 6 illustrates a sensing element of the sensing device of FIG. 5A inmore detail according to an example embodiment;

FIG. 7 illustrates a virtual keyboard arrangement according to anexample embodiment;

FIG. 8A illustrates in plan view a sensing element of the sensing deviceof FIG. 5A in more detail according to an alternative embodiment; and

FIG. 8B is a cross-section view of the sensing device of FIG. 5Acomprising the sensing element of FIG. 8A according to an exampleembodiment of the present disclosure.

For ease of illustration, the various figures are not drawn to scale.

DETAILED DESCRIPTION

Throughout the present description, the term “connected” is used todesignate a direct electrical connection between two elements, whereasthe term “coupled” is used to designate an electrical connection betweentwo elements that may be direct, or may be via one or more othercomponents such as resistors, capacitors or transistors. Furthermore, asused herein, the term “substantially” is used to designate a range of+/−10 percent of the value in question.

FIG. 1 is a cross-section view of a graphene device comprising a film100 of graphene, which is for example just one atom in thickness, or mayhave a thickness of up to 8 atom layers in some embodiments, dependingon the application and the desired electrical conductivity. Inparticular, the graphene film 100 is for example formed of a pluralityof graphene mono-layers attached together. In some embodiments, thegraphene film 100 is doped in order to reduce its surface resistance,for example using P-dopants such as AuCl₃ and/or HNO₃. Additionally oralternatively, layers of one or more dopants such as FeCl₃ may beintercalated between one or more of the graphene layers to reduce theelement resistance. For example, such a technique is described in moredetail in the publication entitled “Novel Highly Conductive andTransparent Graphene-Based Conductors”, I. Khrapach et al., AdvancedMaterials 2012, 24, 2844-2849, the contents of which is herebyincorporated by reference.

In plan view (not represented in FIG. 1 ), the graphene film 100 mayhave any shape, and for example has a surface area of anywhere between 1μm² and 10 cm², depending on application.

The graphene film 100 is covered by a support 102 in the form of a layerof polymer material. The polymer material is for example selected fromthe family of n-xylylenes, and in one example comprises parylene.Parylene has the advantage of being capable of being stretch by up to200% before breaking, and is capable of remaining flexible over arelatively wide temperature range. In one example, the polymer materialcomprises parylene C or parylene N. Both parylene C and parylene N havethe advantage of being relative elastic, while parylene N has a slightlylower Young's modulus, and thus a higher elasticity, than parylene C.

As will be described in more detail below, the polymer support 102 hasfor example been formed by a gas phase deposition technique or by a spindeposition technique. The polymer support 102 for example has athickness of between 10 nm and a few tens or hundreds of μm, or up to 5mm, depending on the application. In some embodiments, the thickness ofthe polymer support 102 could be as low as 5 nm, and for example in therange 5 to 40 nm.

While in the example of FIG. 1 the polymer support is in the form of alayer having a substantially uniform thickness, as will become apparentfrom the embodiments described below, the polymer support could takeother forms, depending on the particular application.

The combination of a graphene film 100 and a polymer support 102provides a multi-layer that can have relatively high electricalconductance while remaining flexible and strong. Of course, while in themulti-layer of FIG. 1 there are just two layers—the graphene layer andthe parylene layer that form a bi-layer, in alternative embodimentsthere could be one or more further layers. For example, the graphenelayer could be sandwiched by parylene layers on each side, and/or one ormore layers of further materials could be formed in contact with thegraphene or parylene layer.

Furthermore, the use of a polymer such as parylene leads to a devicethat is biocompatible, making the device suitable for a variety ofapplications in which it can for example contact human or animal tissue.

FIG. 2 illustrates apparatus 200 for forming a graphene device such asthe device of FIG. 1 according to an example embodiment.

The step of forming the graphene film 100 for example involves formingmono-layers of graphene using the apparatus 200. A similar apparatus isdescribed in the publication entitled “Homogeneous Optical andElectronic Properties of Graphene Due to the Suppression of MultilayerPatches During CVD on Copper Foils”, Z. Han et al., Adv. Funct. Mater.,2013, DOI: 10.1002/adfm.201301732, the contents of which is herebyincorporated by reference.

The apparatus 200 comprises a reaction chamber 202 in which the graphenefilm is formed. For example, the reaction chamber 202 is a tube furnaceor other type of chamber that can be heated.

A substrate 204, for example formed of a copper foil having a thicknessof between 0.1 and 100 μm, is placed within the chamber 202. Thesubstrate 204 provides a surface suitable for graphene formation. Inparticular, the material of the substrate 204 is for example selected asone that provides a catalyst for graphene formation, and for example hasrelatively low carbon solubility. For example, other possible materialsfor forming the substrate 204 include other metals such as nickel,cobalt, or ruthenium or copper alloys such as alloys of copper andnickel, copper and cobalt, copper and ruthenium, or dielectricmaterials, such as zirconium dioxide, hafnium oxide, boron nitride andaluminum oxide. In some embodiments, rather than being a foil, thesubstrate 204 could have a 3D form. The dimensions of such a substrate204 could be anywhere from 0.1 μm to several cm or more. Furthermore,the substrate 204 could be formed on a planar or 3D surface of a furthersubstrate, for example of copper or another material such as sapphire.

An inlet 206 of the reaction chamber 202 allows gases to be introducedinto the chamber, and an outlet 208 allows gases to be extracted fromthe chamber. The inlet 206 is for example supplied with gas by three gasreservoirs 210A, 210B and 210C, which in the example of FIG. 2respectively store hydrogen (H₂), argon (Ar), and methane (CH₄). Inalternative embodiments discussed in more detail below, different gasescould be used. In particular, rather than hydrogen, a different etchinggas, in other words one that is reactive with carbon, could be used,such as oxygen. Rather than argon, another inert gas could be used, suchas helium. This gas is for example used to control the overall pressurein the reaction chamber 202, and could be omitted entirely in someembodiments. Rather than methane, a different organic compound gas couldbe used, such as butane, ethylene or acetylene.

The inlet 206 is coupled to: reservoir 210A via a tube 212A comprising avalve 214A; reservoir 210B via a tube 212B comprising a valve 214B; andreservoir 210C via a tube 212C comprising a valve 214C. The valves 214Ato 214C control the flow rates of the respective gases into the chamber.

The valves 214A to 214C are for example electronically controlled by acomputing device 216. The computing device 216 for example comprises aprocessing device 218, under the control of an instruction memory 220storing program code for controlling at least part of the grapheneformation process.

The outlet 208 is for example coupled via a tube 222 to an evacuationpump 224 for evacuating gases from the reaction chamber 202. The rate ofevacuation by the pump 224 is for example also controlled by thecomputing device 216. As represented by an arrow 226, the computingdevice may also control one or more heating elements of the reactionchamber 202 to heat the interior of the chamber during the grapheneformation process.

A method of forming a graphene film using the apparatus described aboveis for example discussed in more detail in the US patent applicationpublished as US2014/0326700, the contents of which are herebyincorporated by reference.

Furthermore, a deposition chamber 228 is for example provided fordepositing the polymer layer over the graphene film. In the embodimentof FIG. 2 , a trapdoor 230 in one wall of the chamber 202 and apassageway 231 between the chambers 202, 228 permit the substrate 204with graphene film to be transferred between the chambers 202 and 228without being exposed to the atmosphere. In alternative embodiments, thedeposition chambers 202 and 228 could be separate from each other, andthe substrate 204 with graphene film could be transferred without usinga passageway.

The deposition chamber 228 for example comprises an inlet 232 coupledvia a further valve 214D to a supply chamber 234 for providing aprecursor for depositing the polymer material to cover the graphenefilm. The valve is for example controlled by the computing device 216.As mentioned above, the polymer material is for example deposited usinggas phase deposition. The term “gas phase deposition” is considered hereto include physical vapor deposition (PVD), chemical vapor deposition(CVD and atomic layer deposition (ALD). The precursor is for exampleheated in the supply chamber 234 to between 100° C. and 500° C. beforebeing introduced as a vapor phase into the chamber 228 via the valve214D.

FIGS. 3A to 3C are cross-section views of a graphene device during itsfabrication, for example using the apparatus of FIG. 2 .

As shown in the FIG. 3A, initially it is assumed that a graphene film100 has been formed by CVD over a substrate 204, which is for example acopper foil.

FIG. 3B illustrates an operation in which the polymer support isdeposited covering the graphene film 100. In the example of FIG. 3B, thegraphene is deposited over a relatively flat substrate 204, and thepolymer material is deposited as a conformal layer 302 of substantiallyuniform thickness that encapsulates the device, including the substrate204. For example, the device is suspended such that the polymer isdeposited on all faces of the device. Alternatively, the device could beturned over during the deposition process. In yet further alternativeembodiments, the polymer material could be deposited only over thegraphene film 100. Furthermore, rather than being deposited in the formof a layer, the polymer material could be deposited in other forms, aswill be described in more detail below.

FIG. 3C illustrates a subsequent operation in which the substrate 204 isremoved, for example by an etching step or by delaminating the polymerlayer with the graphene film 100 from the substrate 204. For example,the etching step involves removing the polymer coating covering thesubstrate 204, for example using a plasma etch, or by scraping with asharp blade, in order to expose the surface of the substrate. Thesubstrate is then removed, for example using a suitable etch, such as anacid etch or using an electrolysis technique. For example, anelectrochemical delamination process may be performed as described inmore detail in the publication entitled “Electrochemical delamination ofCVD-Grown Graphene Film: Toward the Recyclable Use of Copper Catalyst”,Yu Wang et al., the contents of which is hereby incorporated byreference to the extent permitted by the law.

This leaves the graphene film 100 with the polymer support 102. Thepresent inventors have found that this polymer support 102 not onlyrepairs to some extent any defects in the graphene film 100, but alsolimits further degradation of the graphene film 100 during theseparation of the graphene film 100 from the substrate 204.

An advantage of the process described herein is that no transferoperation is required, reducing the risk that the properties of thegraphene film will be degraded.

Indeed, graphene is generally formed using a chemical vapor deposition(CVD) process, wherein graphene is formed over a base substrate such asa copper foil. However, a difficulty is that it is relatively difficultto remove the graphene layer from the base substrate without damaging orpolluting the graphene layer and/or degrading its conductivity.

By depositing a polymer material by gas phase deposition in contact withthe graphene film, the polymer can remain attached to the graphene whilethe substrate is removed, for example by etching or by a delaminationprocess, without a transfer step.

The process for forming a graphene device as described in relation toFIGS. 3A to 3C may be adapted to form a number of particular graphenedevices as will now be described with reference to FIGS. 4 to 8 .

FIGS. 4A to 4C are cross-section views showing steps in a method offorming a graphene device comprising a three-dimensional graphene filmaccording to an example embodiment. For example, such a device issuitable for being placed on or over a 3D form, such as a human oranimal member, or a device or part of a device, and for example providesthe function of a sensor, of a protection barrier, or the like.

FIG. 4A illustrates an example of a cross-section of a mold 402 overwhich the graphene device is to be formed. The 3D form of this mold 402shown in FIG. 4A is merely one example used for illustration, and manydifferent forms would be possible, depending on the particularapplication. The mold is formed of a material supporting graphenegrowth, such as copper.

FIG. 4B illustrates operations in which a graphene film 100 is formedover the mold 402, and a coating of polymer, such as of parylene, isthen deposited over the graphene film 100.

FIG. 4C illustrates a subsequent operation in which the mold is removed,for example for example by an etching step or by delaminating thepolymer layer with the graphene film 100 from the substrate 204, forexample using a delaminating operation as described above.

FIG. 5A illustrates a sensing device 500, which in this example isdesigned to be worn by a user over their index finger or other bodypart. Of course, the technique that will be represented in relation toFIG. 5A could be applied a variety of different types of sensors havingone or more sleeves or tubes adapted to fit around a body part of ahuman or animal. For example, the sensor could be in the form of a glovewith a sensor in each finger of the glove in order to detect fingermovements.

The sensor device 500 of FIG. 5A comprises a layer of a polymer such asparylene in the form of a sleeve or tube 502 that has dimensions closelyfitting an index finger of a user. In the example of FIG. 5A, the sleeve502 is closed at one end to form a finger. A film of graphene is formedon a portion of the inside surface of the sleeve 502, and provides anelectrode 504 and conductive track 506. The electrode 504 is positionedto contact a portion of the underside of a finger near the tip of thefinger. The electrode 504 is coupled via the conductive track 506 to anend 508 of the sleeve 502 opposite to the fingertip. While not shown inFIG. 5A, the end of the conductive track may be coupled via a wire tomonitoring equipment, or a monitoring device could be implemented by anintegrated circuit mounted on a side of the sleeve 502.

FIGS. 5B to 5D are cross-section views of the sensor device 500 of FIG.5A during process steps for forming the sensor device of FIG. 5A. Thecross-sections of FIG. 5B to 5D for example correspond to a line A-Ashown in FIG. 5A, that passes through a portion of the sleeve 502 closeto the fingertip and passing through the electrode 504.

As represented in FIG. 5B, a finger-shaped mold 510 of the same orapproximately the same dimensions as the index finger to be used in thesensing device 500 is formed, for example of a material that does notsupport graphene growth, such as aluminum oxide. A thin plating 512 of amaterial such as copper, which supports graphene growth, is formed inthe zone in which the electrode 504 and conductive track 506 are to beformed.

For example, in order to form the plated material 508 of copper oranother material, one of two processes could be used.

A first process is for example described in more detail in thepublication by J. Zhang et al. entitled “Electron Beam Lithography onIrregular Surfaces Using an Evaporated Resist”, ACS Nana 2014, 8 (4), pp3483-3489, the contents of which is hereby incorporated by reference tothe extent permitted by the law. According to such a lithographyprocess, an electron or photon sensitive resin is evaporated dependingon the type of lithography to be used and on the desired resolution.Such a resin can be applied to non-planar surfaces in a desired pattern,followed by a lithography operation.

A second process is for example described in more detail in thepublication by J. Chang et al. entitled “Facile electron-beamlithography technique for irregular and fragile substrates”, AppliedPhysics Letters 105, 173109 (2014), the contents of which is herebyincorporated by reference to the extent permitted by the law. Accordingto this technique, a resin film is prepared in advance by spin-coatingand annealing. After this annealing, the resin film becomes solid andflexible, and can be transferred to the non-planar surface and followsit its 3D form. A lithography step can then be performed.

As represented in FIG. 5C, the mold is then for example placed in a CVDchamber such as the chamber 202 of the apparatus of FIG. 2 , and agraphene film 100 is selectively formed over the plating 512. Thepolymer layer in the form of the sleeve 502 is then formed by coating alayer of polymer over the mold, including over the graphene film 100.The polymer coating for example has a thickness of between 50 and 500μm. Where this polymer coating contacts the graphene film 100, itprovides the polymer support for the graphene film 100.

As represented in FIG. 5D, polymer sleeve 502, and the graphene film100, are for example removed from the mold, for example by adelamination process or electrochemical delamination process asdescribed above.

While in the example of FIG. 5A the sensing device 500 comprises asingle graphene conductive track 506 leading to a graphene plate formingthe electrode 504, many other arrangements would be possible, as willnow be described with reference to FIG. 6 .

FIG. 6 illustrates the form of a graphene film 100 of the sensing device500 of FIG. 5A according to one example in which two conductive tracks602, 604 are provided leading to the electrode, and the electrode isimplemented in the form of a meandering track electrically connectingthe track 602 to the track 604 and formed with a detection zone 606. Thetracks 602, 604 and the meandering track are for example formed usingthe lithography or spin-coating process described above with relation toFIG. 5B.

The conductive tracks 602, 604 are for example coupled to a detectioncircuit 608 for detecting a change in resistance of the conductive trackformed in the detection zone. For example, the circuit 608 is adapted toapply a substantially constant current through the conductive tracks602, 604 and to monitor the voltage drop between the conductive tracks602, 604. Pressure applied to the graphene film in the zone 606 forexample causes a change in the resistance of the graphene film bydeforming the graphene film and/or causing a short circuit betweensections of the meandering conductive track. Such a change in theresistance brings about a corresponding change in the voltage across theconductive tracks, which is detection by the detection circuit 608.

In one embodiment, the sensing device of FIG. 6 is used in a key strokedetection system, as will now be described in more detail with referenceto FIG. 7 .

FIG. 7 illustrates a virtual keyboard system in which a projector 702 isprovided, in this example mounted on top of a display 704. The projector702 projects an image 706 of a user interface onto a surface. In theexample of FIG. 7 , the user interface is a keyboard, but in alternativeembodiments, other types of user interface can be projected. Forexample, the screen image could be projected in order to provide thefunctionality of a touch-screen. In such a case, the display 704 couldbe omitted.

The system also for example comprises a 3D ranging camera for detectingtyping events made by a user on the projected image of the keyboard.Such a virtual keyboard system is for example discussed in thepublication by Huan Du et al., entitled “A Virtual Keyboard Based onTrue-3D Optical Ranging”, Proceedings of the British Machine VisionConference, vol. 1, p. 220-229, the contents of which is herebyincorporated by reference to the extent permitted by the law.

A difficulty in such a virtual keyboard system is to confirm a typingevent that has been detected visually. For example, a user may move afinger towards a key position with the intention of making a typingstroke, but then pull-back just short of touching the key position. Sucha non-completed key stroke may be interpreted as an actual key stroke ifbased on visual data alone.

To deal with this problem, the user for example has one or more sensingdevices similar to the ones of FIGS. 5 and 6 attached to one or morefingers. For example, the user wears gloves 708, 710 on their right andleft hands respectively, comprising such a sensing device in one,several or all of its fingers.

While the meandering graphene track of FIG. 6 provides one possiblemeans of detecting an exerted pressure in the detection zone 606, othertechniques may be employed, as will now be described with reference toFIGS. 8A and 8B.

FIG. 8A is a plan view of a sensing apparatus comprising a pair ofgraphene films, respectively comprising conductive track 802 and 804.The conductive track 802 is connected at one end to a graphene plate806, while the conductive track 804 is connected at one end to agraphene plate 808. The graphene plates 806, 808 are arranged such thatthey overlap, and they are separated by a deformable insulating layer(not illustrated in FIG. 8A) such that they have an associatedcapacitance. An external compressive force applied to the plates 806,808, for example caused by a finger hitting a surface, will thus changethe distance between the plates and cause a change in their capacitance,which can be detected by a detection circuit 809 coupled to theconductive tracks 802, 804.

FIG. 8B is a cross-section view of a sensing device 800 similar to thedevice 500 of FIG. 5A, but adapted to comprise the sensing apparatus ofFIG. 8A.

The device 800 for example comprises an outer polymer sleeve 810, havingformed therein the plate 808 and the conductive track 804 (notillustrated in FIG. 8B) running along the length of the sleeve. Such astructure is for example formed by the process described with referenceto FIGS. 5B to 5D. The device 800 also for example comprises an innerpolymer sleeve 812, having formed, on an outer surface thereof, thegraphene plate 806, positioned adjacent to the graphene plate 808, andthe conductive track 802 (not illustrated in FIG. 8B). This structuremay also be formed by the method of FIGS. 5B to 5D, and by then turningthe finger inside-out such that the graphene plate 806 is on the outsideof the inner polymer sleeve 812. The polymer sleeve 812 is thenpositioned as an inner lining of the polymer sleeve 810 to achieve thestructure of FIG. 8B. The graphene plates 806, 808 are separated by aninsulating layer 814 for example formed of polymer, and which maycomprise a polymer coating formed over the graphene plate 806 and/or apolymer coating formed over the graphene plate 808.

In use, the sensing device 800 is placed over a finger or other bodypart. A charge is then for example stored on one of the plates 806, 808by applying a voltage between the conductive tracks 802, 804, forexample by the detection circuit 809. The graphene plates 806, 808 thenform a detection zone such that if pressure is applied in this zone, thecapacitance of the plates 806, 808 will change, causing a change in thevoltage on the conductive tracks 802, 804. This voltage change can bedetected by the detection circuit 809.

An advantage of the graphene device described herein is that the polymerlayer supports the graphene film 100, helping to maintain relative highconductive properties of the graphene film 100 as it is removed from themold.

Furthermore, by depositing the polymer layer using gas phase deposition,the electrical conducting properties and mechanical properties of thegraphene film can be particularly well conserved as the mold is removed.Indeed, gas phase deposition allows a thin polymer coating of relativelyuniform thickness to be applied that has high conformity with theroughness of the surface of the graphene film, by closely following thecontours of the graphene film. In view of its high conformity anduniformity, such a polymer layer exerts a lower stress on the graphenelayer than would be possible with other deposition techniques such asspin coating.

Furthermore, gas phase deposition allows a supporting polymer layer tobe realized that strictly conforms to a 3-dimensional shape of thegraphene film, both at the nanoscale and at the microscale, respectivelyhelping to preserve the integrity of the film by matching the wrinklesand thereby providing good electrical conductivity and helping tomaintain the global 3D shape of the graphene film after the moldremoval, allowing depositions on complex shapes such as gloves, etc.

An advantage of the sensing device described herein is that the polymercoating provides a support layer that remains flexible while holding agraphene electrode in a suitable position for detecting an event such asa key stroke.

Having thus described at least one illustrative embodiment, variousalterations, modifications and improvements will readily occur to thoseskilled in the art.

For example, it will be apparent to those skilled in the art that whilevarious devices comprising graphene have been described above andrepresented in the figures, there are many alternative applications ofthe method of forming the graphene and polymer multi-layer as describedherein.

Furthermore, the various features described in relation to the variousembodiments could be combined, in alterative embodiments, in anycombination.

Such alterations, modifications, and improvements are intended to bewithin the scope of the invention. Accordingly, the foregoingdescription is by way of example only and is not intended as limiting.The invention is limited only as defined in the following claims and theequivalents thereto.

The invention claimed is:
 1. A method of forming a conductive graphenedevice, the method comprising: forming a conductive graphene film over asubstrate, the conductive graphene film consisting essentially of one toeight monolayers of carbon atoms, the conductive graphene film having afirst surface and a second surface, the first surface covering thesubstrate; gas phase depositing a graphene support layer of paryleneover the second surface of the conductive graphene film, the graphenesupport layer of parylene supporting the conductive graphene film duringthe operation of the conductive graphene device; removing the substratefrom the conductive graphene film, thereby exposing the first surface ofthe conductive graphene film; wherein the graphene support layer ofparylene is deposited with a thickness of between 5 nm and 5 mm; whereinthe surface on which the conductive graphene film is formed comprises amold having a shape of a three-dimensional form; and wherein: the moldis formed of a first material and at least one zone of a secondmaterial; during the formation of the conductive graphene film, grapheneselectively forms on the at least one zone of the second material andnot on the first material; and the graphene support layer of parylene isdeposited over the conductive graphene film and at least a portion ofthe first material.
 2. The method of claim 1, further comprising, afterremoving the substrate from the conductive graphene film, performing afurther gas phase deposition of parylene to encapsulate the conductivegraphene film.
 3. A method of forming a conductive graphene device, themethod comprising: forming a conductive graphene film over a substrate,the conductive graphene film consisting essentially of one to eightmonolayers of carbon atoms, the conductive graphene film having a firstsurface and a second surface, the first surface covering the substrate;gas phase depositing a graphene support layer of parylene over thesecond surface of the conductive graphene film, the graphene supportlayer of parylene supporting the conductive graphene film during theoperation of the conductive graphene device; removing the substrate fromthe conductive graphene film, thereby exposing the first surface of theconductive graphene film; wherein the graphene support layer of paryleneis deposited with a thickness of between 5 nm and 5 mm; and wherein theconductive graphene film is deposited to form a conductive track havinga meandering form in a detection zone.
 4. A method of forming aconductive graphene device, the method comprising: forming a conductivegraphene film over a substrate, the conductive graphene film consistingessentially of one to eight monolayers of carbon atoms, the conductivegraphene film having a first surface and a second surface, the firstsurface covering the substrate; gas phase depositing a graphene supportlayer of parylene over the second surface of the conductive graphenefilm, the graphene support layer of parylene supporting the conductivegraphene film during the operation of the conductive graphene device;removing the substrate from the conductive graphene film, therebyexposing the first surface of the conductive graphene film; wherein thegraphene support layer of parylene is deposited with a thickness ofbetween 5 nm and 5 mm; and wherein the conductive graphene film isdeposited in the form of a first plate of graphene formed in a detectionzone and connected to a first conductive track, and wherein the methodfurther comprises: forming a further conductive graphene film covered bya further deposition of the parylene, wherein the further conductivegraphene film is deposited in the form of a second plate of graphene;and assembling the first and second conductive graphene films such thatthe first and second graphene plates form a capacitive interface in thedetection zone separated by a layer of the parylene.